import unittest


def bubble_sort(arr):
    n = len(arr)
    for i in range(n):
        for j in range(0, n - i - 1):
            if arr[j] > arr[j + 1]:
                arr[j], arr[j + 1] = arr[j + 1], arr[j]
    return arr


class TestBubbleSort(unittest.TestCase):
    def test_bubble_sort(self):
        arr = [64, 34, 25, 12, 22, 11, 90]
        result = bubble_sort(arr)
        self.assertEqual(isinstance(result, list), True)
        self.assertEqual(sorted(arr), result)


if __name__ == '__main__':
    unittest.main()